T-cells with anti-tumor potential have shown importance in the application of immunotherapy to treat cancers. The clinical efficacy of non-specific immunomodulatory agents, including immunostimulatory cytokines and antibodies that block negative immunoregulatory molecules or engage agonistic receptors on T-cells, supports the notion that cancer immunity can be manipulated to mediate tumor regression. However, numerous clinical trials administering immunomodulatory agents continue to be halted due to deleterious side effects or worsening of disease. Additionally, the association between intratumoral T-cell accumulation and improved survival in cancer (Zhang et al., 2003, N Engl J Med, 348: 203-13; Galon et al., 2006, Science, 313: 1960-4; Erdag et al., 2012, Cancer Res, 72: 1070-80) predicts a role for tumor-specific T-cell activity in tumor control.
Following antigen-induced stimulation, human T-cells undergo dynamic functional and phenotypic changes, including upregulated surface expression of multiple activation-associated molecules, including CD25, CD69, CD38 and others. The upregulation of surface molecules provides the opportunity to identify and isolate antigen-specific T-cells through antibody binding of the upregulated determinant and subsequent enrichment by magnetic separation or fluorescence-activated cell sorting (FACS).
Immune targeting of tumor antigens that are overexpressed by cancer cells in numerous cancer types with limited expression in normal tissues holds significant promise for widespread clinical application. However, the identification of new immunogenic epitopes from pre-defined antigens or specific tumor types remains a challenge.
To isolate and study naturally-occurring tumor-reactive T-cells, tumors represent a more promising reservoir than blood. An increased relative frequency of defined tumor antigen-specific T-cells reside in tumors (Romero et al., 1998, J Exp Med, 188:1641-50). Unlike in blood, naturally-occurring tumor-reactive T-cells may express activation-associated molecules as a product of direct interaction with tumor cells (Milne et al., 2009, PLoS ONE, 4:e6412).
However, isolation and expansion of tumor-reactive T-cells has been poor at best. Tumor-reactive T cells require activation to express activation-associated molecules on their surfaces. Limited activation of these cells has been achieved with ex vivo stimulation using viral antigens (Wolfl et al., 2007, Blood, 110: 201-10). Stimulation with cytomegalovirus, Epstein-Barr virus, influenza or human adenovirus antigens created reactive T-cells, but the T cells were limited to only virus specific antigens (Zandvliet et al., 2011, J Immunother, 34: 307-19).
Therefore, there is an urgent need in the art for compositions and methods for identifying tumor antigen-specific T-cells and expansion of such cells for the treatment of cancer.